Communication system



A. 1 SPRECKER 210 1,42,l'

COMMUNICATION SYSTEM Filed Jan.v 25, 1935 2 sheets-sheet 1v Dec. 7, 1937.

Dec.7, 1937. A| .'SPRECKER 2,101,421

COMMUNICATI ON SYSTEM Filed Jan. '23, 1935 2 sheets-sheet 2 IN VEN TOR.

@ATTORNEY Patented Dec. 7, 1937 UNITED STATESv PATENT oFFlcE COMMUNICATION SYSTEM Alfred L. Sprecker, Freeport, N. Y.; assigner to International Business Machines Corporation, New York, N. Y., a corporation of New York Application January 23, 1935, SerialNo. 3,001

Claims.

This invention relates to communication systems-and more particularly to printing telegraph systems of the non-synchronous type and applicable to radio transmission.

The type of printing telegraph system embodied in the present invention is similar in principle to the system fully described in the applivalues to which the receiving unit will' give a,

denite and different response to eachsignal.

The system comprises in general a keyboard vor typewriter similar to that of a conventional type- Writer to originate impulses of predetermined current value by depression of the ,particular character key desired to be transmitted. Each character to be transmitted is represented by one or more impulses of differential currentl strength and polarity, the particular signal for a selected character sent averti/ie network when the corresponding key is depressed releasing its pulse wheel or disk suitably provided to send the proper code. Each receiving station includes a galvanometer line relay anda line stepping relay, the former responsive to the denite current strength values and polarity of the impulses, whereas the latter is responsive only to the number of the impulses regardless of the impulse current strength and polarity. f

Due to the particular circuit arrangement embodying the two types of relays just mentioned w ,"ch are' arranged to provide for the conditicnlng of the proper circuit, the proper character is caused to be recorded at the receiving unit.'

The present invention applies the system just' explained to radio transmission. This procedure may#y be effected for example, by transforming thevarous code combinations of impulses representing the signals into separately modulated carrie1\\waves and upon reception interpreting them into code combinations of impulses to separate th E receiving printing telegraph unit in a manner similar to the aforementioned method.

In the/"particular disclosure of the present invention one method of eecting the said translation at the transmitter of combinational pulses .to modulated radio'frequencies to combination pulses at the receiver, will be described and embodies the use of a plurality of different audio frequencies or combination thereof modulating (c1. 17a-s6) 'f the carrier-wave. For illustrative purposes of the above principle, all pulses of positive current may be coded into single audio frequencies; that is, for each increment of positive current values employed, a single audio .frequency for each current value is to be employed, while all negative pulses may be coded as two frequencies, and similarly for each increment of negative current values, a different combination of the double frequencies is .to be employed, and in the combination of which one common audio frequency may' serve as a polarity change for the receiving unit.

In addition thereto the combination code pulses, at the transmitting unit may be impressed upon a circuit including therein,`a polarized relay, 'a rectifier and a multistep galvanometer relay. The polarized relay codes the polarity of the pulses received and lcontrols the transmission of the common frequency that may be used inA addition to the multi-frequencies representing the individual increments of Ycurrent values to represent a definite pulse polarity, let us say a `negative value. The multi-step galvanometer is sensitive to the rectied current pulses yso to translate the diierential current. increments into the corresponding single,audio-frequencies, in addition thereto the galvanometer is responsive to the number of pulses included/in the com- 'bination code to impress the corresponding number of pulses on the carrier wave. Upon reception of the modulated carrier, the plurality of radio vsignals may be impressed upon a circuit including a plurality of tuned circuits, each tuned to a single one of the frequencies em'- ployed. Upon the energization of each tuned circuit, aiazpulse ofa'- corresponding current value is initiated. The reception of the said common frequency employed causes the polarity change of the current impulses and 'upon further description hereinafter it will be understood how these transformed pulses operate the receiving unit in accordance with'the transmitting unit and upon the same principle employed in the said prior application.

The principal object of the present invention is to provide an improved method and apparatus for the transmission-of intelligence.'

ter impulse characteristics.

Further and other objects of the present invention will hereinafter become apparent in the -ac- It is another object of this invention to pro-- vide aprinting telegraph system of radio trans':

companying specication and claims and shown in the drawings. which by way of illustration is what is now considered to be the best mode in which it has been contemplated applying that principle. Other embodiments of the invention employing the same or equivalent principle may be used and structural/changes made as desired by those skilled in the art without' departing from the present invention and Within the spirit of the appended claims.

In the drawings:

Fig. 1 shows one embodiment of the transmitting circuit illustrating the principle of the .invention.

Fig. 2 shows one embodyment of the receiving circuit.

Fig. 3 shows a form of combinational code sys.- tem which may be used 1in conjunction with the system. i 1

-Referring now to the drawings in' which similar' parts are designated by the same numerals in `the several views, it is believed that a clear understanding of the invention will be had therefrom 'when considered in conjunction` with the.

following description.

Transmitting unit -Referring now to Fi y 1, a plurality of pulse wheels or disks I4 are s own with a combination vof conducting segments I6 thereon. The arrangement and number of conducting segments for each disk corresponds to the code shown in Fig. 3, for example, the character S the code of which is current value l, positive potential and four impulses, namely, three short and one long. Therefore, on the disk I4 for the character S four conducting segments I6 are disposed thereon sothat the three short pulses of current are conducted before lie long segment engages the contacts I1. to transmit the long impulse of its corresponding current value. It is to be noted .that for characters represented by Va plurality of limpulses the last impulse is always a long one the signicance of which will be understood as the descriptionprogresses. Each disk therefore has disposed thereupon the number of segments to correspond to the number of impulses in its particular code. It is sufcient to mention that upon the depression of a character key of the typewriter (not shown) its corresponding sk I4 is released to complete one revolution, the eby con,- ducting the proper increment of current value, polarity and the number of impulses to'fthe line I9 representing the character. A further descrip tion may be hadby referring to the said prior application in which the transmitting typewriter and mechanism for releasing the pulse wheels is shown and -completely described.

The combinatlonal" code of impulses are impressed on circuit I9 comprising a polarized relay 20 adapted to be energized by negative currents so as` to positionA its armature 50 in vengagement withcontact 5I, positive current returns the armature toits normal position as shown in the figure. Also connected to circuit L9 is the bridge rctiiier unit 52 which in turn is connected to the coil 53 of the multi-step galvanometer relay 54, so-that the positive Vand negative current values become uni-directional currents energizing .the

relay coil 53 in degree corresponding to the current values. Four diti'erentcurrent values are shown in the code in` Fig. 3, and the impression fof these current values onthe relay coil 53 posl-,

Since this mechanism forms 'no part of the invention, it. is deemed unnecessary to repeat such description.,

tions its armature 55 in engagement with one of the four contacts 5B shown in Fig. 1 to complete a circuit from the radio transmitter and ampli-l ier 5l through conductor 58, armature 55, cor responding contact 5B and frequency generator 59 of any well known type and return conductor 50 modulating the carrier wave accordingly. Galvanometer relay 54 is also sensitive to the number of impulses transmitted by the released code disk so that the particular contact 55 is en'- gaged'a number of times corresponding to the number of impulses transmitted so that the radio signal consists of the similar number of pulses. 'I'he receiving appartus is so designed that it is not effected by the contacts 55 for the short interval of time they are engaged by armature 55 while it is positioned inaccordance with the current value impressed on the relay coil. Upon energization of relay 20 so that its 'contact 5I is c ed it is seen that the circuit 6I is closed to conn t the frequency generator 59 designated f-5 to the transmitter, the purpose of which will be understood as the description progresses.

Therefore, let it be assumed, that the typewriter key corresponding to the letter"fS is depressed. It is understood that its designated pulse wheel I4 is released to send four impulses, three short and one" long impulses of current value 1 and positive polarity to the circuit Isn.` The bambination of the diiferent frequencies comprising the signal to be transmitted is shown in Fig. 3, for the letter S frequency vf---I is designated. Since the polarity of the impulses impressed on relay 20 are positive, the relay remains inoperative. The relay coil 53 connected to circuit I 9 is energized so that its armature 55 engages the contact I ofthe group of contacts 56 to impress the particular frequency f-I upon the radio transmitter 51. Since four impulses were sent out by the code wheel I4, yrelaycoil 53 is energized four times to impress the frequency f--I for fourI timed intervals on the transmitter, the iirst three intervals of time shorter than the last in accordance with the code for character S, In this manner the radio signal-is transmitted for this character consisting of three short and one long pulses of a definite frequency value.

For the character O a long impulse of Jcurrent value 4 and negative polarity is sent out on circuit I9 by its pulse wheel. vThis impulse causes the relay 20 to be operated to close the circuit so as to modulate the carrier wave by frequency 1*--5`andv frequency f-4, since the relay coil 53 is energized4 by current value. 4 to position its armature to the contact 4 for one long interval of time; the radio signal for this 'character consists of one pulse of the combination of frequencies L44 and f-5.`.

'I'he method of translating the transmitted signals will now be explained intconnection with Fig. 2. j.'

I Receiving unit l A The various signals are iinpressed upon the receiver and amplifier 55 in tlie well known manner to energize thecircuit 68 comprising a-plurality of filters 51, each one responsiveV to the individual frequencies f.-| tof-5. Connected to each illter circuit 61 is an individual relay R-I to R-5 adapted to be operated by its corresponding vconnected circuit and frequency therefor. Operation of the relays R-I to R-4 connects the battery 58 to the circuit 69 to impress diierent current values thereon in'accordance with the operation o1' a particular relay R-l to R-4. Relay R--I impresses a current value 1 upon the said circuit, relay R-2, value '2, etc. Similarly, if the relays Rf-l to Rf-4 are operated a number of times, the similar number of impulses of the particular current value are impressed on circuit 69.` y Operation of relay `lita-5 by a signal comprising the frequency f-5 acts as a regular pole-changer and transfers the negative side of the battery B8 from contact 10 v.

reversed to position the armature 24 of galvanometer relay 2| accordingly. It is to be noted that this relay 2 i has eight contact positions and is adapted to position its armature on its contacts 23-1 to 4 in accordance with the current values 1 to 4 impressed on its coil'25.

The direction .of movement of the armature is governed by the polarity of the current as indicated in the figure.` This galvanometer relay is sensitive to the current values and polarity but n ot to the number of impulses transmitted and adjusted so that the short impulses are not of sufficient duration to position its amature 24. However, the long impulse which is the last impulse transmitted in the selected code is of sufcient duration to cause the amature 24 to engage its proper contact 23 corresponding to the current value and polarity selected by the relays R--l to llt-4. Therefore, when and only when the long impulse is impressed on this selecting circuit is the relay 2l sufllciently energized to be properly positioned so that the armature 24 can supply current to the conditioned circuits through its particular contact 23, a complete disclosure of which is set forth in the said prior application and therefore, the, following brief explanation thereof is deemed sufiicient. i Relay 22 Aconnected to the circuit 69 is responsive onLv to the number of impulses transmitted and closes its contact 26 for each impulse (short and long) to conduct current from positive battery through lines 21 and 28, contact 26, line`30,

coil 3l, of stepping relay designated 32, normally closed contact 33A and line 34 tonegative battery stepping relay 32 is adapted to step its brush or 'armature 33 ahead to the adjacent contact 36 each time its coil 3l is energized. The additional coil 39 is adapted to return the brush 33 to its normal position as shown in the figure whenever it is energized.

Therefore, for each impulse transmitted, the

relay 22 is energized, energizing relay 32 ,to step its brush arm 33 Iahead so as to engage contacts 36 successively and corresponding to the number of impulses transmitted.

Depending on the number of short and long impulses transmitted, the brush arm 33 will be h'eld in constant engagement with its particular contact 36 so that the proper selection of the particular circuit may be made. The final position of the arm 33 during the transmission of a signalis actually the summation of the number of independent impulses received. .The brush arm maintains this last position mentioneduntil the partieularietcer con :s isgseiecrwedenuenergized tourecordfthecharaeteremegtypewriter at the receiving unit is of the type equipped with -solenoids and adapted upon-the energization of the solenoid-to have the key bar depressed'lto operate the corresponding type bar accordingly.'

When the character is recorded relay 40 and coil 39 of relay 32 are energized to release the brush arm 33 and restore it to normal position as indicated in the gure. The energization of relay 40 causes its normally closed contact 33A to be opened and in this manner preventing back circuits to be set up through contacts 36 when the arm 33 is returned to normal position.

It was mentioned hereinbefore that the last impulse for each character is a long impulse,l or Where the character is represented by a single impulse, this impulse is always of long duration, so that it is seen that the brush arm 33 is always engaging its last 'corresponding contact 36 when the galvanometer relay 2| is energized to correctly position its armature 24, and for this reason the proper Selection of the character lztter coil 38 may be made as follows.

side of the line, energizing relay 43 to close its contacts 44 whereupon current is conducted from the source through lines 21 and 45, contact 44,

' coil of relay 46 to negative side of the line, energizing relay 46 to close its contacts 41. The contacts 41 are arranged so that upon energization, contacts 41a., 41h, 41e, and 41d which are connected to the individual letter coil circuits close immediately to energize its respective coil. Contact 41e is arranged to close a timed interval later; this timed interval is equivalent to the time required to energize letter coils 38, when the contacts 41a tod are closed sufliciently to cause the" character to be recorded. In practice, this interval is equal to a fraction ofa second so that special relay equipment is not necessary to obtain this time delay.

Contact 41e then closes when the energized letter coils 38 cause the character to be recorded, toconduct current from the source through lines 21 and 48, contact 41e, line 49, lines 5I) and 5I, coil 39 of relay 32, and `coil of relay 49, line 34 to the other side of the line, energizing relays 39 and 40 restoring brush arm 33 to normal position.

A specific example will now be given namely for the character S, the code of which is 4 impulses, three short and one long impulses of the first increment value and positive polarity.

It was explained how depression of the character key S at the transmitting unit caused the release of the pulse wheel I4 for one revolution to impress the impulses on circuit I9, and how the galvaiometer relay 63 effected transmission of the radio signal of the four pulses of frequency f-I. It was also explained how relay R.-|. is energized by the tuned circuit 61 sensitive only to frequency f-I to initiate at the receiver three short and one long impulses of current value 1 and positive polarity, and impress these impulses on circuit 69.

Relay 22 is energized four times to close its contact 26 accordingly, energizing stepping relay '32 four times to position its brush arm 33 on its contact 4. The first three impulses are of short duration and therefore are not sumcient to energize galvanometerrelay 2| to position contact arm 24 on its proper contact. However, the impulse of longer duration causes the arm 24 to engage contact l of relay 2| of the positive group of contacts, since the' current strength is of the first increment value and positive polarity. Relay 43 is now energized, closing its contact 44 to energize selector group relay 46 and close its contacts 41a, 41h, 41o, and 41d'. l

Brush arm 33 of relay 32 has been positioned to its contact 4, so that when contacts 41 close, a circuit is established through letter coil 38 representing S to be energized to cause a record to be made of the said character. Immediately upon recording the character S, contact 41e is closed to energize coil-39 of relay 32 and relay 40 causing the contact arm 33 to be reset to normal position and condition the circuits so as to enable other character selections corresponding to the characters transmitted.

Similarly, for the character O the code of which is a long impulse of current value 4, negative polarity and a combination of frequencies f4 and -5.

It was described how the frequencies are transmitted to impress the signal on circuitGB (Fig. 2). Relays R-4 and R-5 are energized to initiate an impulse of current value 4 and negative polarity. It was explained how relay R5 reversed the battery connections upon energization to reverse the direction of the current flow in circuit 69.

The polarized relay 20 at the transmitter may be adjusted sc as not to be sensitive to the number of impulses impressed on circuit I9, so that when four impulses, let us say, are impressed on the said circuit, relay 20 is slow to release and not responsive to the short timedA interval of deenergization between transmission of the impulses so that the frequency f-S during the entire timed interval required to transmit the signal, would be impressed on the carrier wave and maintain relay R-S at the receiver energized for this period when signals representing negative polarity are transmitted, and in this manner insure that only negative pulses are impressed on circuit 69.

When the said impulse representing character O is impressed on circuit 69, relay 2| is energized to position the arm 24 on contact 4 of the negative group of contacts, energizing the correspending relay 43 and relay 46 to close its contacts 41a to d. Also stepping relay 32 was energized to step its arm 33 to contact .I, thereby establishing a circuit through the letter coil 38 representing O to record this character in a manner explained hereinbefore.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a single'modication, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention. It is the intention therefore to be limited only as indicated by the scope of the following claims.

What is claimed is as follows:

1. ,In a communication system, means to initiate character signals consisting of impulses having di'erent current values and polarity, a plurality of sources of different frequencies, means to select certain frequencies from the said plu- -rality in accordance lwith the current values of the initiated signals to modulate a carrier wave accordingly, means adapted to control the selection of one of said frequencies in addition to other selected frequencies to represent a denite polarity, means to transmit and receive the modulated carrier wave, means associated with the receiving means to transform the carrier wave modulated means for modulating a carrier wave in accordance with the said initiated impulses, means to transmit and receive the modulated wave, a plurality of circuits corresponding to the said signals, means associated with the receivingmeans to transform the modulated wave into signals consisting of code combinations of impulses having predetermined characteristics to correspond to the initiated impulses, and means responsive to the impulse characteristics and to the number of impulses included in the code to select from the plurality of circuits those which correspond to the initiated signals. v

3. In a printing telegraph system, means for initiating character signals consisting of .code combinations of impulses having different current values and polarity, a source of a plurality of different frequencies, means to translate said signal code combinations into code combinations of said frequencies-receiving means adapted toretranslate said code combinations of frequencies into said original code of impulses having difierent current values and polarity, and a Work circuit selectively controlled by the last mentioned impulses of the original code.

4. The invention set forth in claim 3 in which means are provided to control the selection of an additional frequency representing a definite polarity of the impulses and thereby controlling the said receiving means in re-translating the code combinations of frequencies so that the polarity of the said last mentioned impulses corresponds lto the said initiated impulses.

5. In a communication system, means for initiating signals consisting of code combinations of impulses having predetermined characteristics comprising different current values and polarity,

` a source of a plurality of different frequencies,

means to translate said signal code combinations into code combinations of said frequencies, receiving means adapted to re-translate said code combinations of frequencies into said original code of impulses having predetermined characteristics, and means responsive to and controlled selectively by and in accordance with. the impulse characteristics and the number of impulses included in said code.

6. The invention set forth in claim 3 in which the said translating means includes a selective, multi-position relay device to control the selection of the said frequencies.

7. The invention set forth in claim 3 in which the said receiving means includes a plurality of electrically tuned circuits for the different frequencies whereby each tuned circuit energized controls the operation of an individual relay device.

8. The method of transmitting and receiving printing telegraph signals which comprises initiating character signals having diiferent current values and polarity and number of impulses, translating said initiated character signals into various frequencies or combinations thereof, transmitting the said frequencies or combinations thereof to a receiving station, translating the said frequencies into the original character signals different current Values and polarity, translating said initiated code combinations ofl'impulses into code combinations of various frequencies,4 transmitting said frequencies to a receiving station,

' translating the said frequencies into the original code combinations of impulses having the said predetermined characteristics and selecting particular circuits from a plurality of circuits in accordance with the last mentioned impulse characteristics and number of impulses in said code.

10. The method or transmitting and receiving character signals which comprises initiating signals consisting of code combinations of impulses having predetermined characteristics (comprising different current values and polarity, translating said initiated code combinations of impulses into various frequencies or combinations thereof,

= transmitting the said frequencies to a receiving station, translating the said frequencies into the original codecombinations of impulses having the said predetermined characteristics, selecting particular circuits from a plurality of circuits in accordance with the last mentioned code combinations of impulses and energizing the selected circuits upon receipt of a predetermined impulse.

ALFRED L. SPRECKER. 

